JP5531967B2 - Glass for scattering layer of organic LED element and organic LED element - Google Patents

Description

  The present invention relates to glass, in particular, glass used for a scattering layer of an organic LED element, and an organic LED element using the glass.

The organic LED element has an organic layer. And there exists a bottom emission type which takes out the light produced | generated by the organic layer from a transparent substrate.
Here, the amount of light that can be extracted outside the organic LED element is also less than 20% of the emitted light.
Therefore, there is a document describing that a scattering layer made of glass is provided in an organic LED element to improve light extraction efficiency (Patent Document 1).
In recent years, environmental pollution has become a serious problem in melting glass containing lead oxide. Accordingly, the glass is required not to contain lead oxide.

Japanese Special Table of Publication 2004-513383

  However, Patent Document 1 has a problem that the content of the glass composition is not disclosed or suggested, and cannot be implemented.

Scattering layer glass of an organic LED element of one embodiment of the present invention, as represented by mol% based on _oxides, P ₂ O 5: _{15~30% and,} Bi ₂ O 3: _5~25% and, _Nb 2 O ₅ : 5 to 27% and ZnO: 15 to 35%, and the total content of alkali metal oxides composed of Li ₂ O, Na ₂ O, and K ₂ O is 5% by mass or less. It is characterized by that.
An organic LED element of one embodiment of the present invention includes a transparent substrate, a first electrode provided on the transparent substrate, an organic layer provided on the first electrode, and a second electrode provided on the organic layer. the provided, further, by mol% based on _oxides, P ₂ O 5: and _15~30%, Bi ₂ O 3: and _{5~25%, Nb 2 O 5:} 5~27% and, ZnO: 10 It is characterized by having a scattering layer containing ˜35% and containing a total amount of alkali metal oxides composed of Li ₂ O, Na ₂ O and K ₂ O of 5% by mass or less.

  ADVANTAGE OF THE INVENTION According to this invention, the organic LED element using the glass of the scattering layer used for an organic LED element, or its scattering layer can be provided.

Sectional drawing of the 1st organic LED element of this invention Sectional drawing of the 2nd organic LED element of this invention Graph showing the relationship between the refractive index of ITO and the refractive index of glass for scattering layer Top view showing the structure of a device having a scattering layer Top view showing the structure of an element without a scattering layer Graph showing the relationship between voltage and current Graph showing the relationship between luminous flux and current Conceptual diagram of a system for evaluating the angular dependence of light emission Graph showing the relationship between brightness and angle Graph showing the relationship between chromaticity and angle

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the figure, corresponding parts are indicated by corresponding reference numerals. The following embodiment is shown as an example, and various modifications can be made without departing from the spirit of the present invention.

(Organic LED element)
First, the organic LED element of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a first organic LED element of the present invention. The first organic LED element of the present invention is a bottom emission type organic LED element. The first organic LED element of the present invention includes a transparent substrate 110, a scattering layer 120 formed on the transparent substrate 110, a first electrode 130 formed on the scattering layer 120, and the first electrode 130. The organic layer 140 is formed on the organic layer 140, and the second electrode 150 is formed on the organic layer 140. In the first organic LED element of the present invention, the first electrode 130 is a transparent electrode (anode), and the second electrode 150 is a reflective electrode (cathode). The first electrode 130 has transparency for transmitting light emitted from the organic layer 140 to the scattering layer 120. On the other hand, the second electrode 150 has reflectivity for reflecting light emitted from the organic layer 140 and returning it to the organic layer 140.

  FIG. 2 is a cross-sectional view of a second organic LED element of the present invention. The second organic LED element of the present invention is a double-sided emission type organic LED element. The second organic LED element of the present invention includes a transparent substrate 110, a scattering layer 120 formed on the transparent substrate 110, a first electrode 130 formed on the scattering layer 120, and the first electrode 130. The organic layer 140 is formed on the organic layer 140, and the second electrode 210 is formed on the organic layer 140. In the second organic LED element of the present invention, the first electrode 130 is a transparent electrode (anode), and the second electrode 210 is a transparent electrode (cathode). The first electrode 130 has transparency for transmitting light emitted from the organic layer 140 to the transparent substrate 110. On the other hand, the second electrode 210 has transparency for transmitting light emitted from the organic layer 140 to a surface opposite to the surface facing the organic layer 140. This organic LED element is used as an illumination application in which light is emitted from the front and back surfaces.

  Hereinafter, as a representative, each configuration of the first organic LED element will be described in detail. In addition, it cannot be overemphasized that what has provided the same code | symbol in the 1st and 2nd organic LED element has the same structure or the same function.

(Transparent substrate)
As the light-transmitting substrate used for forming the transparent substrate 110, a material having a high visible light transmittance, such as a glass substrate, is mainly used. Specifically, a material having a high transmittance is a plastic substrate in addition to a glass substrate. Examples of the material of the glass substrate include inorganic glass such as alkali glass, non-alkali glass, and quartz glass. In order to prevent the diffusion of the glass component, a silica film or the like may be coated on the surface of the glass substrate. Examples of the plastic substrate material include polyester, polycarbonate, polyether, polysulfone, polyethersulfone, polyvinyl alcohol, and fluorine-containing polymers such as polyvinylidene fluoride and polyvinyl fluoride. Note that in order to prevent moisture from permeating through the substrate, the plastic substrate may have a barrier property. The thickness of the transparent substrate is preferably 0.1 mm to 2.0 mm in the case of glass. However, since strength will fall when too thin, it is especially preferable that it is 0.5 mm-1.0 mm.

(Scattering layer)
The scattering layer 120 is formed by forming glass powder on a substrate by a method such as coating and baking at a desired temperature, and is dispersed in the base material 121 having the first refractive index and the base material 121. And a plurality of scattering materials 122 having a second refractive index different from that of the base material 121. In the plurality of scattering materials 122, the distribution of the scattering materials in the scattering layer is reduced from the inside of the scattering layer to the outermost surface. The scattering layer is made of glass, so that it has excellent scattering characteristics while maintaining the smoothness of the surface. By using it on the light-emitting surface side of light-emitting devices, extremely efficient light extraction is possible. Can be realized.

  As the scattering layer, glass (base material) having a high light transmittance is used. A plurality of scattering substances (for example, bubbles, precipitated crystals, material particles different from the base material, and phase-separated glass) are formed inside the base material. Here, the particle refers to a small solid substance such as a filler or ceramic. Air bubbles refer to air or gas objects. Moreover, phase-separated glass means the glass comprised by two or more types of glass phases.

  In order to improve the light extraction efficiency, the refractive index of the base material is preferably equal to or higher than the refractive index of the first electrode. This is because when the refractive index is low, a loss due to total reflection occurs at the interface between the base material and the first electrode. The refractive index of the base material only needs to exceed at least a part of the emission spectrum range of the organic layer (for example, red, blue, green, etc.), but exceeds the entire emission spectrum range (430 nm to 650 nm). It is more preferable that it exceeds the entire wavelength range of visible light (360 nm to 830 nm). Note that the refractive index of the first electrode may be higher than the refractive index of the base material as long as the difference between the refractive index of the base material and the refractive index of the first electrode is within 0.2.

  Moreover, in order to prevent the short circuit between the electrodes of an organic LED element, the scattering layer main surface needs to be smooth. For this purpose, it is not preferable that the scattering material protrudes from the main surface of the scattering layer. In order that the scattering material does not protrude from the main surface of the scattering layer, it is preferable that the scattering material does not exist within 0.2 μm from the main surface of the scattering layer. The arithmetic average roughness (Ra) defined in JIS B0601-1994 of the main surface of the scattering layer is preferably 30 nm or less, more preferably 10 nm or less (see Table 1), and particularly preferably 1 nm or less. Both the scattering material and the base material may have a high refractive index, but the difference in refractive index (Δn) is preferably 0.2 or more in at least a part of the emission spectrum range of the light emitting layer. In order to obtain sufficient scattering characteristics, the difference in refractive index (Δn) should be 0.2 or more over the entire emission spectrum range (430 nm to 650 nm) or the entire visible wavelength range (360 nm to 830 nm). More preferred.

In order to obtain the maximum refractive index difference, it is desirable that the base material has a high refractive index glass and the scattering material has a gaseous object, that is, a bubble.
By giving the base material a specific transmittance spectrum, the color of light emission can be changed. As the colorant, known ones such as transition metal oxides, rare earth metal oxides and metal colloids can be used alone or in combination.
Here, in general, it is necessary to emit white light in a backlight or lighting application. Whitening is a method of spatially painting red, blue, and green (painting method), a method of laminating light emitting layers having different emission colors (lamination method), and providing blue light that is separated spatially. A method (color conversion method) for performing color conversion with a color conversion material is known. In backlight and lighting applications, a white layer can be obtained uniformly, so a lamination method is common. The light emitting layer to be stacked uses a combination that turns white by additive color mixing. For example, a blue-green layer and an orange layer may be stacked, or red, blue, and green may be stacked. In particular, for lighting applications, color reproducibility on the irradiated surface is important, and it is desirable to have a necessary emission spectrum in the visible light region. When the blue-green layer and the orange layer are laminated, the green light emission intensity is low, and therefore, when a light containing a lot of green is illuminated, the color reproducibility is deteriorated. While the lamination method has an advantage that it is not necessary to spatially change the color arrangement, it has the following two problems. The first problem is that since the organic layer is thin, the extracted emitted light is affected by interference. Therefore, the color changes depending on the viewing angle. In the case of white, such a phenomenon may be a problem because the sensitivity to the color of human eyes is high. The second problem is that the carrier balance is shifted while the light is emitted, the light emission luminance of each color is changed, and the color is changed.

  In the organic LED element of the present invention, a fluorescent material can be used as a scattering material or a base material. Therefore, the effect of changing the color by performing wavelength conversion can be brought about by the light emission from the organic layer. In this case, the light emission color of the organic LED can be reduced, and the emitted light is scattered and emitted, so that the angle dependency of the color and the temporal change of the color can be suppressed.

(First electrode)
The first electrode (anode) is required to have a translucency of 80% or more in order to extract light generated in the organic layer 140 to the outside. In addition, a high work function is required to inject many holes. _{Specifically, ITO (Indium Tin Oxide),} SnO 2, ZnO, IZO (Indium Zinc Oxide), AZO (ZnO-Al 2 O 3: aluminum zinc oxide _{doped), GZO (ZnO-Ga 2} O ₃ : zinc oxide doped with gallium), Nb-doped TiO ₂ , Ta-doped TiO ₂ and other materials are used. The thickness of the anode is preferably 100 nm or more. The refractive index of the anode 130 is 1.9 to 2.2. Here, when the carrier concentration is increased, the refractive index of ITO can be lowered. In the case of commercially available ITO, SnO ₂ has a standard of 10 wt%. From this, the refractive index of ITO can be lowered by increasing the Sn concentration. However, although the carrier concentration increases as the Sn concentration increases, there is a decrease in mobility and transmittance. Therefore, it is necessary to determine the amount of Sn by balancing these.

  Here, although it demonstrated as a 1st electrode mainly used with a bottom emission type organic LED element, it cannot be overemphasized that it is good also as what is used with a double-sided emission type organic LED element.

(Organic layer)
The organic layer 140 is a layer having a light emitting function, and includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. The refractive index of the organic layer 140 is 1.7 to 1.8.
The hole injection layer is required to have a small difference in ionization potential in order to lower the hole injection barrier from the anode. Improvement of the charge injection efficiency from the electrode interface in the hole injection layer lowers the drive voltage of the device and increases the charge injection efficiency. Polyethylene dioxythiophene (PEDOT: PSS) doped with polystyrene sulfonic acid (PSS) is widely used for polymers, and phthalocyanine-based copper phthalocyanine (CuPc) is widely used for low molecules.
The hole transport layer serves to transport holes injected from the hole injection layer to the light emitting layer. It is necessary to have an appropriate ionization potential and hole mobility. Specifically, the hole transport layer may be a triphenylamine derivative, N, N′-bis (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPD ), N, N′-diphenyl-N, N′-bis [N-phenyl-N- (2-naphthyl) -4′-aminobiphenyl-4-yl] -1,1′-biphenyl-4,4 ′ -Diamine (NPTE), 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (HTM2) and N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 '-Diphenyl-4,4'-diamine (TPD) or the like is used. The thickness of the hole transport layer is preferably 10 nm to 150 nm. The thinner the thickness is, the lower the voltage can be. However, the thickness is particularly preferably 10 nm to 150 nm from the problem of short circuit between electrodes.

  The light-emitting layer uses a material that provides a field where injected electrons and holes are recombined and has high emission efficiency. More specifically, the light emitting host material and the light emitting dye doping material used in the light emitting layer function as recombination centers of holes and electrons injected from the anode and the cathode, and light emission to the host material in the light emitting layer The doping of the dye obtains high luminous efficiency and converts the emission wavelength. These are required to have an appropriate energy level for charge injection, to form a uniform amorphous thin film having excellent chemical stability and heat resistance.

In addition, it is required that the type and color purity of the luminescent color are excellent and the luminous efficiency is high. Light emitting materials that are organic materials include low-molecular materials and high-molecular materials. Further, it is classified into a fluorescent material and a phosphorescent material according to the light emission mechanism. Specifically, the light emitting layer is composed of tris (8-quinolinolato) aluminum complex (Alq ₃ ), bis (8-hydroxy) quinaldine aluminum phenoxide (Alq ′ ₂ OPh), bis (8-hydroxy) quinaldine aluminum— 2,5-dimethylphenoxide (BAlq), mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex (Liq), mono (8-quinolinolato) sodium complex (Naq), Mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex, mono (2,2,6,6-tetramethyl-3,5-heptanedionate) sodium complex and bis ( 8-quinolinolato) calcium complex (CAQ ₂₎ metal complexes of quinoline derivatives such as tetraphenyl butadiene, off Nirukinakudorin (QD), anthracene, and a fluorescent substance such as perylene and coronene. As the host material, a quinolinolate complex is preferable, and an aluminum complex having 8-quinolinol and a derivative thereof as a ligand is particularly preferable.

The electron transport layer serves to transport electrons injected from the electrode. Specifically, the electron transport layer includes a quinolinol aluminum complex (Alq ₃ ), an oxadiazole derivative (for example, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND) and 2 -(4-t-butylphenyl) -5- (4-biphenyl) -1,3,4-oxadiazole (PBD) and the like), triazole derivatives, bathophenanthroline derivatives, silole derivatives and the like are used.
The electron injection layer is required to increase the electron injection efficiency. Specifically, the electron injection layer is provided with a layer doped with an alkali metal such as lithium (Li) or cesium (Cs) at the cathode interface.

(Second electrode)
For the reflective electrode (cathode) as the second electrode, a metal having a small work function or an alloy thereof is used. Specific examples of the cathode include alkali metals, alkaline earth metals, metals of Group 3 of the periodic table, and the like. Of these, aluminum (Al), magnesium (Mg), silver (Ag), or alloys thereof are preferably used because they are inexpensive and have good chemical stability. In addition, a laminated electrode in which Al is vapor-deposited on a co-deposited film of Al, MgAg, a thin film deposited film of LiF or Li ₂ O, or the like is used. In the polymer system, a laminate of calcium (Ca) or barium (Ba) and aluminum (Al) is used. Needless to say, the reflective electrode may be used as an anode.
Here, when the second electrode is used in the second organic LED element of the double-sided emission type, it is not reflective but requires translucency. Therefore, the configuration and characteristics at that time are preferably the same as those of the first electrode.

(Glass for scattering layer)
Next, the scattering layer glass of the organic LED element of the present invention will be described in detail.
Since the refractive index of the glass for a scattering layer is preferably equal to or higher than the refractive index of the translucent electrode material as described above, it is desirable that it be as high as possible. The glass transition temperature of the glass for the scattering layer is desirably as low as possible in order to prevent thermal deformation of the substrate when the glass powder is fired and softened to form the scattering layer. In addition, the thermal expansion coefficient of the glass for the scattering layer must be close to or slightly lower than the thermal expansion coefficient of the substrate in order to prevent the phenomenon of cracking or warping due to stress generated between the scattering layer and the substrate. There is. In general, the glass having a high refractive index and a low transition temperature has a coefficient of thermal expansion that is much larger than the coefficient of thermal expansion of the substrate. Therefore, it is desirable that the coefficient of thermal expansion of the glass for the scattering layer be as low as possible. Warpage and cracking become a major obstacle when forming a translucent electrode layer on a scattering layer.

Represented by mol% based on oxides of the present _invention, P ₂ O 5: _{15~30% and,} Bi ₂ O 3: and _{5~25%, Nb 2 O 5:} 5~27% and, ZnO: 10 to 35 %, And the total content of alkali metal oxides composed of Li ₂ O, Na ₂ O, and K ₂ O is 5% by mass or less.
P ₂ O ₅ is a component that forms a network structure serving as a skeleton of the glass and stabilizes the glass, and is essential. When P ₂ O ₅ is less than 15 mol%, devitrification is likely to occur. 19 mol% or more is preferable, and 20 mol% or more is more preferable. On the other hand, when it exceeds 30 mol%, it is difficult to obtain a high refractive index. 28 mol% or less is preferable and 26 mol% or less is more preferable.
Bi ₂ O ₃ is a component that imparts a high refractive index and increases the stability of the glass, and is essential. If it is less than 5%, the effect becomes insufficient. 10 mol% or more is preferable and 13 mol% or more is more preferable. On the other hand, when it exceeds 25 mol%, the thermal expansion coefficient is increased, and the coloring is easily increased. 23 mol% or less is preferable and 20 mol% or less is more preferable.
Nb ₂ O ₅ is a component that imparts a high refractive index and lowers the thermal expansion coefficient, and is essential. If it is less than 5 mol%, the effect becomes insufficient. 7 mol% or more is preferable and 10 mol% or more is more preferable. On the other hand, when it exceeds 27 mol%, the glass transition temperature is increased and devitrification is likely to occur. 20 mol% or less is preferable and 18 mol% or less is more preferable.
ZnO is a component that greatly lowers the glass transition temperature and increases the refractive index while suppressing an excessive increase in the thermal expansion coefficient, and is essential. If it is less than 10 mol%, the effect becomes insufficient. 16 mol% or more is preferable and 18 mol% or more is more preferable. On the other hand, if it exceeds 35 mol%, the devitrification tendency of the glass increases. 30 mol% or less is preferable and 27 mol% or less is more preferable. In addition, although it does not necessarily respond | correspond one-to-one with mol% notation, when expressed in mass%, 7 mass% or more is preferable.
Alkali metal oxides composed of Li ₂ O, Na ₂ O and K ₂ O may increase the thermal expansion coefficient. Therefore, it is preferable not to contain substantially (content is substantially zero). However, since it has the effect of giving the glass devitrification resistance and lowering the glass transition temperature, it may be contained up to 7 mol%.

Here, the alkali metal may move when an electric field is applied in a humid state, and may destroy the terminal of the organic LED element. Therefore, the total amount of the alkali metal oxide is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably substantially not contained (the content is substantially zero).
Further, Na ₂ O and _{K 2} O, since the result in particularly large thermal expansion coefficient compared to Li ₂ O, if the inclusion of alkali metal oxides, substantially free of Na ₂ O and _{K 2} O (Content is almost zero), it is preferable to use only Li ₂ O.
TiO ₂ tends to devitrify as the glass transition temperature rises. Therefore, it is preferable that TiO ₂ is not substantially contained (the content is substantially zero). However, since it has an effect of imparting a high refractive index, it may be contained up to 8 mol%.
B ₂ O ₃ is not essential, but has an effect of improving the solubility of the glass. Therefore, you may contain to 17 mol%. However, if it exceeds 17 mol%, devitrification and phase separation are likely to occur, and it becomes difficult to obtain a high refractive index.
WO ₃ is not essential, but has the effect of imparting a high refractive index without significantly changing the thermal expansion coefficient and glass transition temperature. Therefore, you may contain to 20 mol%. However, when it exceeds 20 mol%, coloring increases and devitrification easily occurs.
TeO ₂ is not essential, but has an effect of lowering the glass transition temperature while suppressing an excessive increase in the thermal expansion coefficient. Therefore, you may contain to 7 mol%. However, it is expensive and may erode the platinum crucible, so it is preferable not to use a large amount.
GeO ₂ is not essential, but has an effect of imparting a high refractive index. Therefore, you may contain to 7 mol%. However, since it is expensive, it is preferable not to use a large amount.
Sb ₂ O ₃ is not essential, but it is not only effective as a clarifying agent but also has an effect of suppressing coloring. Therefore, you may contain to 2 mol%.
Alkaline earth metal oxides (MgO, CaO, SrO, BaO) are not essential, but have the effect of improving the stability of the glass. Therefore, you may contain to 10 mol%. However, if the content exceeds 10 mol%, the refractive index is lowered and the thermal expansion coefficient is increased.
In addition, it does not contain substantially when it does not contain substantially, and includes the case where it mixes as an impurity by other ingredients origin.

The glass of the present invention is SiO ₂ , Al ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , ZrO ₂ , Ta ₂ O ₃ , Cs ₂ O, as long as the effects of the invention are not lost. Transition metal oxides and the like can also be contained. Their total content is preferably less than 5 mol%, more preferably less than 3 mol%, and particularly preferably substantially no content (the content is almost zero).
In addition, since the glass of this invention does not contain lead oxide substantially, possibility of causing environmental pollution is low.
The glass of the present invention uses raw materials such as oxides, phosphates, metaphosphates, carbonates, nitrates, and hydroxides, weighs them so as to have a predetermined composition, mixes them, platinum, etc. Can be obtained by melting at a temperature of 950 to 1500 ° C. using a crucible of No. 1 and casting into a mold or pouring into a gap between twin rolls and quenching. Also, it may be gradually cooled to remove the distortion. The glass produced by the above method is used in the form of powder. The glass powder is obtained by pulverizing glass with a mortar, ball mill, jet mill or the like, and classifying it as necessary. The weight average particle size of the glass powder is typically 0.5 to 10 microns. The surface of the glass powder may be modified with a surfactant or a silane coupling agent.
This glass frit is kneaded with a solvent or a binder as necessary, and then applied onto a transparent substrate and fired at a temperature about 60 ° C. higher than the glass transition temperature of the glass frit to soften the glass frit and cool to room temperature. By doing so, a transparent substrate with a scattering layer is obtained. As the solvent, α-terpineol, butyl carbitol acetate, phthalate ester, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, etc., and as the binder, ethyl cellulose, acrylic resin, styrene resin, Examples thereof include phenol resin and butyral resin. In addition, you may contain components other than a solvent or a binder in the range which does not impair the objective of this invention. In addition, when using a binder, before softening a glass frit, it is preferable to include the process of baking at a temperature lower than a glass transition temperature and vaporizing a binder.

Tables 1 to 3 show the composition of the glass expressed in mol% in each example, the refractive index (n _d ), the glass transition temperature (T _g ), and the average thermal expansion coefficient from 50 ° C. to 300 ° C. ( α _50-300 ). In addition, the composition in terms of mass% converted based on the composition in terms of mol% is also shown. In any glass, oxides, metaphosphates or carbonates are used as raw materials for each component. After vitrification, the raw materials are weighed so as to have the composition shown in Table 1 and mixed sufficiently, and then a platinum crucible is used. After melting in a temperature range of 950 ° C. to 1350 ° C. in an electric furnace, it is cast into a carbon mold, the cast glass is cooled to a transition temperature, immediately put into an annealing furnace, and gradually cooled to room temperature. Got.
The resultant glass refractive index _(n d), the glass transition temperature _(T g), the thermal expansion coefficient of from 50 ° C. to 300 ° C. The (alpha _50-300) was measured as follows.
(1) Refractive index (n _d )
After polishing the glass, it was measured by a V-block method using a precision refractometer KPR-2000 manufactured by Kalnew.
(2) Glass transition temperature (T _g )
The glass was processed into a round bar shape having a diameter of 5 mm and a length of 200 mm, and then measured with a thermomechanical analyzer (TMA) TD5000SA manufactured by Bruker AXS Co., Ltd. at a heating rate of 5 ° C./min.
(3) Thermal expansion coefficient from 50 ° C. to 300 ° C. (α _50-300 )
The glass was processed into a round bar shape having a diameter of 5 mm and a length of 200 mm, and then measured with a thermomechanical analyzer (TMA) TD5000SA manufactured by Bruker AXS Co., Ltd. at a heating rate of 5 ° C./min. When the length of the glass rod at 50 ° C. is L ₅₀ and the length of the glass rod at 300 ° is L ₃₀₀ , the thermal expansion coefficient (α _50-300 ) from 50 ° C. to 300 ° C. is α _{50 -300} = determined by _{{(L 300 / L 50)} -1} / (300-50).

    Here, Examples 1 to 22 are examples.

The flaky glasses having the respective compositions shown in Examples 2 and 3 were weighed, mixed and melted in the same manner as described above, and then the melt was poured into a gap between twin rolls and rapidly cooled. Each flake was dry pulverized with an alumina ball mill for 1 hour to obtain each glass frit. Each glass frit had a mass average particle size of about 3 microns. 75 g of each obtained glass frit was kneaded with 25 g of an organic vehicle (10% by mass of ethyl cellulose dissolved in α-terpineol) to prepare a glass paste. This glass paste is printed on a 10cm square and 0.55mm thick soda lime glass substrate surface-coated with a silica film, and uniformly printed in the center with a 9cm square size so that the film thickness after firing is 30μm. This was dried at 150 ° C. for 30 minutes, then returned to room temperature, heated to 450 ° C. in 30 minutes, held at 450 ° C. for 30 minutes, then heated to 550 ° C. in 12 minutes and 550 ° C. For 30 minutes, and then cooled to room temperature in 3 hours to form a glass frit fired layer on a soda lime glass substrate. And about each, it was observed whether the fired layer and the crack of the board | substrate had generate | occur | produced, and the average value of the curvature of the board | substrate in the four corners of the fired layer was measured. The results are shown in Table 4. The thermal expansion coefficient (α _50-300 ) from 50 ° C. to 300 ° C. of the soda lime glass used is 83 × 10 ⁻⁷ / K.

  As is apparent from the above, the glass for the scattering layer of the organic LED element of the present invention is suitable as a scattering layer for the organic LED element because it has good adhesion to the substrate and does not cause problems such as warping and cracking. I understand that.

Next, a confirmation experiment for improving the light extraction efficiency will be described.
First, soda lime glass manufactured by Asahi Glass Co., Ltd. was used as the glass substrate. The scattering layer was produced as follows. First, powder raw materials were prepared so that the glass composition was as shown in Table 5.

Thereafter, the prepared powder raw material was dissolved in an electric furnace at 1050 ° C. for 90 minutes, held at 950 ° C. for 60 minutes, and then cast into a roll to obtain glass flakes. This glass has a glass transition temperature of 475 ° C., a yield point of 525 ° C., and a thermal expansion coefficient of 72 × 10 ⁻⁷ (1 / ° C.) (an average value of 50 to 300 ° C.). The measurement was performed by a thermal expansion method using a thermal analyzer (manufactured by Bruker, trade name: TD5000SA) at a heating rate of 5 ° C./min. The refractive index nF at the F line (486.13 nm) is 2.00, the refractive index nd at the d line (587.56 nm) is 1.98, and the refractive index nC at the C line (656.27 nm) is 1. .97. The measurement was performed with a refractometer (trade name: KPR-2000, manufactured by Kalnew Optical Industry Co., Ltd.).

  The prepared flakes were pulverized with a planetary mill made of zirconia for 2 hours, and then sieved to obtain glass powder. The particle size distribution at this time was D50 of 2.15 μm, D10 of 0.50 μm, and D90 of 9.72 μm. Next, 35 g of the obtained glass powder was kneaded with 13.1 g of an organic vehicle (a solution of ethyl cellulose in α-terpineol or the like) to prepare a glass paste. This glass paste was uniformly printed on the above-mentioned glass substrate so as to have a circular shape with a diameter of 10 mm and a film thickness after firing of 14 μm. And after drying this for 30 minutes at 150 degreeC, it returned to room temperature once, heated up to 450 degreeC in 45 minutes, hold | maintained and baked at 450 degreeC for 30 minutes. Thereafter, the temperature was raised to 580 ° C. in 13 minutes, held at 580 ° C. for 30 minutes, and then lowered to room temperature in 3 hours. In this way, a scattering layer was formed on the glass substrate.

In order to evaluate the characteristics of the glass substrate with a scattering layer thus prepared, haze measurement and surface waviness measurement were performed.
For haze measurement, a haze computer (trade name: HZ-2) manufactured by Suga Test Instruments Co., Ltd. was used, and a single glass substrate was used as a reference sample. That is, the total light transmittance is 100 and the haze is 0 when a single glass substrate is measured. As a result of measurement, the total light transmittance was 79, and the haze value was 52.

  Next, surface waviness was measured. The apparatus uses a surface roughness measuring machine manufactured by Kosaka Laboratory Ltd. (table name: Surfcorder ET4000A), the evaluation length is 5.0 mm, the cutoff wavelength is 2.5 mm, and the measurement speed is 0.1 mm / The roughness was measured with s. As a result, the arithmetic average roughness Ra was 0.55 μm, and the arithmetic average wavelength λa was 193 μm. These numerical values are based on the ISO 4287-1997 standard.

  Next, the above-mentioned glass substrate with a scattering layer and a glass substrate without a scattering layer were prepared, and an organic EL element was produced. First, ITO having a thickness of 150 nm was formed by DC magnetron sputtering as a translucent electrode. At the time of sputtering, a film is formed in a desired shape using a mask. In addition, the refractive index of ITO and the refractive index of the glass for scattering layers described above are shown in FIG. In the figure, the vertical axis represents the refractive index, and the horizontal axis represents the wavelength (unit: nm). Subsequently, ultrasonic cleaning using pure water and IPA was performed, and then the surface was cleaned by irradiating ultraviolet rays with an excimer UV generator. Next, α-NPD (N, N′-diphenyl-N, N′-bis (l-naphthyl) -l, l′ biphenyl-4,4 ″ diamine: CAS No. 123847 is used using a vacuum deposition apparatus. -85-4) was deposited to a thickness of 100 nm, Alq3 (tris8-hydroxyquinoline aluminum: CAS No. 2085-33-8) to 60 nm, LiF to 0.5 nm, and Al to 80 nm. At this time, α-NPD and Alq3 form a circular pattern having a diameter of 12 mm using a mask, and LiF and Al form a pattern using a mask having a 2 mm square region on the ITO pattern through the organic film. The element substrate was completed.

  Then, the concave substrate was partially formed by performing sandblasting on a separately prepared glass substrate (PD200 manufactured by Asahi Glass Co., Ltd.) to create a counter substrate. Photosensitive epoxy resin was applied to the bank around the recess for sealing the periphery.

  Next, the element substrate and the counter substrate are placed in a glove box in a nitrogen atmosphere, and a water catching material containing CaO is attached to the concave portion of the counter substrate, and then the element substrate and the counter substrate are bonded together and irradiated with ultraviolet rays. Then, the peripheral sealing resin was cured to complete the organic EL element.

  4 and 5 show how the element emits light. Here, FIG. 4 shows an element having a scattering layer, and FIG. 5 shows an element without a scattering layer. In the figure, 400 represents a scattering layer, 410 represents an organic layer, 420 represents an ITO pattern, and 430 represents an Al pattern. In the element without the scattering layer, light emission is confirmed only from the approximately 2 mm square region formed by the crossing of the ITO pattern and the Al pattern. However, in the element fabricated on the scattering layer, not only the above approximately 2 mm square region. It can be seen that light is also extracted from the surrounding scattering layer forming portion into the atmosphere.

Thereafter, the optical characteristics of the element were evaluated.
First, Hamamatsu Photonics EL characteristic measuring machine C9920-12 was used for the total luminous flux measurement. FIG. 6 shows current-voltage characteristics of an element with and without a scattering layer. In the figure, the vertical axis represents voltage (unit: V), and the horizontal axis represents current (unit: mA). Thus, almost the same characteristics are obtained, and it can be seen that a large leak current does not exist even in the element formed on the scattering layer. Next, the current luminous flux characteristics are shown in FIG. In the figure, the vertical axis indicates the luminous flux (unit: lm), and the horizontal axis indicates the current (unit: mA). As described above, the amount of light flux is proportional to the current regardless of the presence or absence of the scattering layer. Furthermore, it was confirmed that the element having the scattering layer had a 51% increase in the luminous flux compared to the element having no scattering layer. As shown in FIG. 3, since the refractive index of the scattering layer is higher than the refractive index of ITO, which is a translucent electrode, at the emission wavelength of Alq3 (470 nm to 700 nm), the EL emission light of Alq3 is scattered with ITO. Suppressing total reflection at the interface of the layers, indicating that light is efficiently extracted into the atmosphere.

Next, the angle dependency of light emission was evaluated. For the measurement, using a color luminance meter (trade name: BM-7A) manufactured by Topcon Techno House Co., Ltd., as shown in FIG. The angle dependence of the luminescent color was measured. In the figure, 800 indicates an evaluation element, and 810 indicates a spectrometer. At the time of measurement, a current of 1 mA is applied to the element to light it. As shown in FIG. 8, the angle is defined as a measurement angle θ [°], which is an angle formed between the normal direction of the element and the direction from the element toward the luminance meter. That is, the state where the luminance meter is installed in front of the element is 0 °. The luminance data obtained from the measurement is shown in FIG. In the figure, the vertical axis represents luminance (unit: cd / m ² ), and the horizontal axis represents angle (unit: °). Further, chromaticity data obtained from the measurement is shown in FIG. In the figure, the vertical axis represents V ′ and the horizontal axis represents U ′. Here, the CIE1976UCS color system is used to calculate the chromaticity coordinates.

  It can be seen from the luminance data in FIG. 9 that the luminance is higher at any measurement angle as compared with the case where there is no scattering layer. Furthermore, when the total luminous flux was calculated by integrating these luminance data at each solid angle, it was confirmed that the luminous flux amount was increased by 54% compared to the case where there was no scattering layer. This is almost the same as the measurement result obtained by the above-described total luminous flux measurement apparatus, and also shows that the luminous flux of the element is greatly improved by the scattering layer.

  Next, it can be seen from the chromaticity data in FIG. 10 that the chromaticity changes greatly depending on the measurement angle in the element without the scattering layer, whereas the change is small in the element with the scattering layer. From these results, it was found that by adding a scattering layer to the element, in addition to the effect of improving the light extraction efficiency, which is the original purpose, a further effect of reducing the color angle change can be obtained. The fact that the change in the color angle is small is a great advantage that the viewing angle is not limited for the light emitting element.

  This application is based on a Japanese patent application filed on Jan. 26, 2009 (Japanese Patent Application No. 2009-014332), the contents of which are incorporated herein by reference.

110 Transparent substrate 120 Scattering layer 130 First electrode 140 Organic layer 150, 210 Second electrode

Claims (10)

In mol% display based on oxide,
And P ₂ O ₅ 15~30%,
Bi ₂ O ₃ 5-25%,
Nb ₂ O ₅ 5 to 27%,
ZnO 4 to 35%,
A glass for a scattering layer of an organic LED element, wherein the total content of alkali metal oxides composed of Li ₂ O, Na ₂ O, and K ₂ O is 5% by mass or less.   2. The glass for a scattering layer of an organic LED element according to claim 1, wherein the total content of the alkali metal oxide is 2% by mass or less.   The glass for a scattering layer of an organic LED element according to claim 1, wherein the glass does not substantially contain the alkali metal oxide. The glass for a scattering layer of an organic LED element according to any one of claims 1 to 3, wherein the glass contains substantially no TiO ₂ content.   The glass for a scattering layer of an organic LED element according to any one of claims 1 to 4, wherein the glass does not substantially contain a lead oxide content. An organic LED element comprising a transparent substrate, a first electrode provided on the transparent substrate, an organic layer provided on the first electrode, and a second electrode provided on the organic layer. And
As represented by mol% based on _oxides, P ₂ O 5: and _15~30%, Bi ₂ O 3: and _5~25%, Nb ₂ O 5: and 5 to 27%, ZnO: a 4-35% An organic LED element comprising a scattering layer containing and containing an alkali metal oxide composed of Li ₂ O, Na ₂ O, and K ₂ O in a total amount of 5% by mass or less.   The organic LED element according to claim 6, wherein the scattering layer is provided on the transparent substrate.   The organic LED element according to claim 6, wherein the scattering layer is provided on the organic layer.   The organic LED element according to any one of claims 6 to 8, wherein the first and second electrodes are transparent electrodes.   The organic LED element as described in any one of Claim 6 to 9 used for illumination.

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